Levels of DNA and/or hemoglobin pyridyloxobutylation were compared in A/J mice or F344 rats treated with a single dose of [5-3H]4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone ([5-3H]NNK),[5-3H]4-hydroxy-1-(3-pyridyl)-1-butanone ([5-3H]4-HPB) or [5-3H]4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone ([5-3H]NNKOAc), a compound that generates the proposed pyridyloxobutylating agent in situ upon esterase hydrolysis. The lung and liver DNA samples isolated from A/J mice treated with the various compounds were subjected to acid hydrolysis and the hydrolysates were analyzed for the presence of [5-3H]4-HPB No detectable levels were found in the lung DNA isolated from [5-3H]4-HPB-treated animals, whereas significant amounts of [5-3H]4-HPB were released from lung and liver DNA isolated from [5-3H]NNKOAc-treated mice. The levels of total binding and [5-3H]4-HPB released from the globin isolated from these animals showed a similar trend. That is, low binding levels were detected in the globin isolated from [5-3H]4-HPB-treated animals and significantly higher levels of binding were detected in the globin from the [5-3H]NNKOAc-and [5-3H]NNK treated animals. Comparable findings were obtained in the rat experiments. These studies clearly demon strate that methyl hydroxylatlon of NNK leads to a species that is capable of reacting covalently with nucleophiles in DNA and protein. Thus, the levels of 4-HPB released from DNA and globin can be attributed to the activation of NNK and not to the direct binding of 4-HPB.
Bibliographical noteFunding Information:
The authors wish to thank the staff of the AHF Research Animal Facility for conducting the animal experiments and Dr S.Amin's group at AHF for supplying the NNK and myosmine. This study was supported by grants no. 44377 and 29580 from the National Cancer Institute. This is paper no. 4 in the series 'Hemoglobin adducts as carcinogen dosimeters'.